Field of Invention
The present invention relates to a field of permanent magnetic device, and more particularly to a method for producing a neodymium-iron-boron rare earth permanent magnetic device having a high performance.
Description of Related Arts
Neodymium-iron-boron rare earth permanent magnetic materials are widely applied in the nuclear magnetic resonance imaging of medical industry, hard disk drivers of computers, loudspeaker boxes, mobiles, etc., because of its excellent magnetic property. To meet the requirements of energy-saving and the low carbon economy, the neodymium-iron-boron rare earth permanent magnetic materials are applied in fields of auto parts, household appliances, energy-saving and controlling motors, hybrid electric vehicles, wind power generation, etc.
In 1982, Japan Sumitomo Special Metals Co. firstly published Japanese patents about the neodymium-iron-boron rare earth permanent magnetic materials, i.e., JP1,622,492 and JP2,137,496, and then Japan Sumitomo Special Metals Co. applied for United States patents and European patents. The characteristic, ingredients, and producing method of the neodymium-iron-boron rare earth permanent magnetic materials were disclosed. The main phase is Nd2Fe14B phase, and the grain boundary phases are Nd-rich phase, B-rich phase, and impurities comprising rare earth oxides.
On Apr. 1, 2007, Japan Hitachi Metals Co. was merged with Japan Sumitomo Special Metals Co., and took up the rights and obligations of the patent licenses of the neodymium-iron-boron rare earth permanent magnetic materials of Japan Sumitomo Special Metals Co. On Aug. 17, 2012, Japan Hitachi Metals Co. submitted a case to United States International Trade Commission (ITC), based on the fact that Japan Hitachi Metals Co. owns the U.S. Pat. No. 6,461,565, U.S. Pat. No. 6,491,765, U.S. Pat. No. 6,537,385, and U.S. Pat. No. 6,527,874 applied in United States.